Polycarbonate resins, which are excellent in transparency, heat resistance and impact resistance, are widely used in optical media fields, electrical, electronic and OA fields, automobile fields, industrial machinery fields, medical treatment fields and other industrial fields. However, since polycarbonates generally used are produced from petroleum-derived raw materials, concerns over depletion of petroleum resources and an increase in the amount of carbon dioxide in air which causes global warming can be enumerated. Thus, biomass resources, which do not depend on oil as a raw material and effect carbon neutral, which means that the resources do not increase the amount of carbon dioxide even when burnt, are attracting a lot of attention. In the field of polymers, the development of biomass plastics produced from the biomass resources is now actively under way.
Of these, as an amorphous polycarbonate resin obtained from a biomass resource and having high heat resistance, a polycarbonate resin produced from a raw material obtained from an ether diol residue which can be produced from sugar has been contemplated. Especially, polycarbonates containing isosorbide as a monomer have features such as excellent transparency, heat resistance, weathering resistance and pencil hardness, and contemplation has been under way by making use of these features (PTLs 1 and 2).
The above-described polycarbonate resin is generally used in combination with various stabilizers, depending on its applications (PTLs 3 to 5). For example, in PTL 3, addition of a hindered amine-based optical stabilizer as a weather resistance formulation to a copolymer of isosorbide and an alicyclic diol monomer reduces haze increase and yellowness index after weathering resistance test. In PTL 4, a formulation of a colorant and a hindered amine-based optical stabilizer is adopted in a copolymer of isosorbide and an alicyclic diol monomer, which reduces color change and physical property degradation after weathering resistance test. In PTL 5, a formulation of a hindered amine-based optical stabilizer is used in a polymer alloy of an aliphatic polycarbonate, which is a copolymer of isosorbide and an alicyclic diol monomer and an aromatic polycarbonate composed of bisphenol A, improving the color change after weathering resistance test.
As aforementioned, as a weather resistance formulation for a polycarbonate containing isosorbide, hindered amine-based optical stabilizers are widely used. Unfortunately, such a hindered amine-based optical stabilizer is a basic compound and may lead to a concern about acceleration of hydrolysis when contained in a polycarbonate resin. The basicity of a hindered amine-based stabilizer is attributable to its structure, on which the degree of the weathering resistance and the basicity depend. Thus, to combine hydrolytic resistance and weathering resistance, it is necessary to take these factors into consideration. In use for exterior applications, further improvements are required.